libertas: remove duplicated #include

Remove duplicated #include('s) in
  drivers/net/wireless/libertas/cfg.c
Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/cfg.c

@@ -9,8 +9,6 @@
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <linux/slab.h>
-#include <linux/sched.h>
-#include <linux/wait.h>
 #include <linux/ieee80211.h>
 #include <net/cfg80211.h>
 #include <asm/unaligned.h>